The present invention relates to industrial process pressure transmitters. More particularly, the present invention relates to isolator plugs of isolator mounting assemblies for supporting a pressure sensor and for isolating the pressure sensor and an interior cavity of the transmitter from a process line fluid to be measured.
Industrial process control systems are used to monitor and control industrial processes which produce or transfer liquids or the like. In such systems, it is typically important to measure “process variables” such as temperatures, pressures, flow rates, and others. Process control transmitters are used to measure such process variables and transmit information related to the measured process variable back to a central location such as a central control room.
One type of process variable transmitter is a pressure transmitter which measures pressures, or pressure differences between two pressures, of process fluids and provides an output related to the pressures or pressure differences. In the case of differential pressures, the pressure difference may, in turn, represent a flow rate, a level of process fluid in a vessel, or other process variable. The transmitter is configured to transmit information related to the pressures or differential pressures back to the central control room. The transmission is typically sent over a two wire process control loop; however, other communication techniques may be used, including wireless techniques.
To measure such pressures, the pressures must be coupled to the process variable transmitter through some type of process coupling. For example, the process fluid can comprise a component used in an industrial process such as natural gas, oil, etc. In industrial process pressure transmitters, isolator mounting assemblies used to isolate a pressure sensor from the fluid to be measured in a process line are known. Typically, the isolator mounting assembly mounts at the base of a transmitter housing in a hole that opens to an interior cavity of the transmitter. An isolation plug of the isolator mounting assembly provides a capillary tube to transfer the process pressures to the pressure sensor, while the interior cavity protects known circuitry that connects to the pressure sensor in order to obtain a signal proportional to the pressure in the process line. Since some process fluids are highly corrosive, some process transmitters are required to use isolation plugs made from materials which are known to be resistant to corrosion or damage from these corrosive process fluids. Such corrosion resistant materials, such as Alloy C-276, add significantly to the material cost of the process transmitter.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.